Radio synchronization technique

ABSTRACT

The present disclosure relates to methods and devices for synchronizing one or more radio devices with a radio access node. A method of providing synchronization with a radio access node for radio communication to one or more radio devices is disclosed. The method comprises or triggers transmitting a configuration message to at least one of the radio devices, where the configuration message is indicative of a synchronization signal configuration for a configurable synchronization signal. The method further comprises or triggers transmitting the configurable synchronization signal to the at least one radio device in accordance with the synchronization signal configuration and communicating one or more decodable signals between the radio access node and the at least one radio device using radio resources in accordance with the configurable synchronization signal. A corresponding method of synchronizing the radio device with the radio access node for radio communication is disclosed.

TECHNICAL FIELD

The present disclosure generally relates to a technique forsynchronizing participants in a radio communication. More specifically,and without limitation, methods and devices are provided forsynchronizing one or more radio devices with a radio access node.

BACKGROUND

In order to wirelessly connect to a network with defined time structure,e.g., a scheduled radio access network (RAN), a radio device performsnetwork synchronization (briefly: synchronization). The synchronizationincludes adjusting the frequency of the radio device relative to the RANand finding the proper timing of the RAN. In existing cellular RANs,such as Long Term Evolution (LTE) specified by the 3rd GenerationPartnership Project (3GPP), the radio device (e.g., a user equipment orUE) performs synchronization based on a primary synchronization signal(PSS) and a secondary synchronization signal (SSS).

The PSS allows for network detection with a high frequency error, up totens of ppm. Additionally, the PSS provides a network timing reference.In 3GPP LTE, Zadoff-Chu (ZC) sequences are used as PSS signals. ZCsequences are of constant amplitude and appear in both time domain andfrequency domain. Thus, a ZC sequence may be multiplexed in thefrequency domain together with other data and detected in the timedomain, allowing for a simplified detector. Three different sequencesare used as the PSSs, which allow for an initial cell identificationwith reasonable complexity, e.g. by correlating the received signal inthe time domain with each of the three known sequences. 3GPP LTE systemstransmit one PSS in one Orthogonal Frequency-Division Multiplexing(OFDM) symbol every 5 subframes or 70 OFDM symbols, i.e., every 5 ms.When the UE has no information about the timing of the PSStransmissions, such as at initial access (i.e., at initial cell search)or after a considerable timing drift when not having a sustainedconnection to the RAN, the UE must have its receiver turned on for 5 msto guarantee not to miss a PSS transmission, even if the PSS itself lastonly for about 70 μs.

The SSS allows for more accurate frequency adjustments and channelestimation while at the same time providing fundamental information ofthe RAN. In 3GPP LTE implementations, maximum length sequences (MLSs orm-sequences) are used for the different SSSs. In total 168 basic SSSsequences are defined in order for the RAN to use PSS and SSS torepresent in total 504 cell IDs. Having detected the SSS, the UE maycontinue to read the Physical Broadcast Channel (PBCH) in order toidentify and receive the master information block (MIB) followed by thesystem information blocks (SIBs), namely SIB 1 and SIB 2, prior toperforming random access. The SSS is also transmitted in one OFDM symbolevery 5 subframes or 70 OFDM symbols, i.e., every 5 ms.

Conventionally, in order to resynchronize to the RAN, a radio device mayuse both the PSS and the SSS. Assuming that no movement has occurred,the underlying PSS sequence and SSS sequence are already known. In thecase of limited mobility, the radio device may rely on information aboutits neighboring cells. By using both sequences, the radio device hastwice as many samples for a time domain correlation operation comparedto the case when only one of the two were used.

However, since only two symbols out of 70 OFDM symbols (i.e., 5subframes each comprising 14 OFDM symbols) in a 5 ms interval are usedfor the synchronization, channel conditions with extremely lowsignal-to-noise ratios (SNRs) require averaging over multiplesynchronization signals (PSSs and/or SSSs), which is a very expensiveoperation due to the sparse transmission of the synchronization signals.Machine-to-Machine (M2M) is an important use case with such low SNRs. Upto 640 synchronization signals or even more can be necessary for worstsituations, which implies synchronization durations of almost twoseconds. From a power consumption perspective, this is extremely costly,and a significant limitation in device longevity.

While initial access synchronization may be as costly as a laterresynchronization, the initial access synchronization is typically onlyperformed once, whereas resynchronization may be performed regularlygain and again, e.g., with a periodicity of tens of seconds. Hence, interms of time and energy consumption, resynchronization poses asubstantial problem.

The evolution of radio communication techniques, e.g. in the frameworkof 3GPP for a New Radio (NR) technique, aim at meeting M2M and Internetof Things (IoT) related use cases. Most recent work for 3GPP LTEReleases 13 and 14 include enhancements to support Machine-TypeCommunication (MTC) devices with specific device categories, namelyCat-M1 and Cat-M2, supporting a reduced bandwidth of 6 physical resourceblocks (PRBs) and up to 24 PRBs for Cat-M2, as well as enhancements tosupport Narrowband IoT (NB-IoT) devices using a specific radio interfacewith specific device categories, namely Cat-NB1 and Cat-NB2.

Such enhancements may be regarded as enhancements to LTE. Herein, theenhancements introduced in 3GPP Releases 13, 14 and 15 for MTC arecollectively referred to as enhanced MTC or eMTC, including (withoutlimitation thereto) the support for bandwidth-limited devices such asCat-M1 and the support for coverage enhancements. Moreover, the termeMTC may be used to distinguish M2M uses cases from other NB-IoT usescases, which term is here used for any 3GPP Release, although thefeatures supported by eMTC and NB-IoT are similar on a general level.

There are multiple differences between existing LTE and the proceduresand channels defined for eMTC and for NB-IoT. Some important differencesinclude specific physical channels, such as the physical downlinkcontrol channels referred to as MPDCCH for eMTC devices and NPDCCH forNB-IoT devices, as well as a specific physical random access channelreferred to as NPRACH for NB-IoT devices.

Objectives for 3GPP Release 15, relating to both NB-IoT and eMTC, for aneven further enhanced MTC (also referred to as efeMTC) according to thedocument 3GPP RP-170732 for 3GPP TSG RAN Meeting #75, include improvinglatency, namely reducing system acquisition time (particularly for cellsearch and/or system information including MIB and SIB1 with bandwidthreduction, SIB1-BR) and acquisition performance, optionally also forconnected mode DRX.

Power consumption reduction for physical channels in idle mode pagingand/or connected mode DRX is a further objective. The 3GPP TSG RAN1Meeting #90 agreed on the working assumption that, for idle mode, apower saving physical signal shall indicate whether the UE needs todecode subsequent physical channels for idle mode paging.

Improving latency and improving power consumption are related in thatboth depend on the synchronization prior to executing further tasks.However, the conventional synchronization for existing LTE wasoriginally developed for mobile broadband applications, which did notconsider the extremely low SNRs relevant for MTC. Hence, for lower SNRs,the existing synchronization is a cumbersome task. The UE needs multiplerepetitions of the synchronization signal in order to receive itcorrectly, while the synchronization signals are transmitted relativelyseldom with one PSS and one SSS every 5 subframes or 5 ms, which leadsto an inacceptable consumption of time and energy for thesynchronization.

SUMMARY

Accordingly, there is a need for a synchronization technique thatreduces energy consumption or latency in at least some situations.Alternatively, or more specifically, there is a need for a techniquethat efficiently synchronizes radio devices with different radioconditions or capabilities without compromising network overhead.

As to one aspect, a method of providing synchronization with a radioaccess node for radio communication to one or more radio devices isprovided. The method comprises or triggers a step of transmitting aconfiguration message to at least one of the radio devices, theconfiguration message being indicative of a synchronization signalconfiguration for a configurable synchronization signal. The methodfurther comprises or triggers a step of transmitting the configurablesynchronization signal to the at least one radio device in accordancewith the synchronization signal configuration. The method furthercomprises or triggers a step of communicating one or more decodablesignals between the radio access node and the at least one radio deviceusing radio resources in accordance with the configurablesynchronization signal.

At least some embodiments of the technique provide a configurablesynchronization signal. The configurable synchronization signal may alsobe referred to as a resynchronization signal or a configurableresynchronization signal, e.g., because the configurable synchronizationsignal may be not the first synchronization signal used by the radiodevice and/or may be not the only synchronization signal received by theradio device for synchronization with the radio access node. Thetechnique is applicable to machine-to-machine (M2M) communication. Sameor further embodiments exchange data in a radio communication involvingdiscontinuous reception (DRX). Particularly, the method may beimplemented for controlling, e.g., by the RAN, power supply andsynchronization of a receiver at the radio device.

The decodable signals may be encoded with data. The data may compriseuser data or control data (e.g., control signaling). At least in someembodiments, the decodable signals may be a physical signal that can beefficiently decoded and/or detected prior to decoding further controlsignaling.

The synchronization signal may be implemented using a specific channel.The synchronization signal or the channel may be defined in terms oftime and/or frequency resources and/or spatial streams according to thesynchronization signal configuration.

The term radio device may encompass a device for machine-typecommunication (MTC), an enhancement thereof (eMTC), a device fornarrowband Internet of things (NB-IoT) applications or a broadbanddevice. In the context of a 3GPP implementation, without being limitedthereto, the radio device may also be referred to as a user equipment(UE).

The one aspect of the technique may be implemented at the RAN, e.g., atthe node.

As to another aspect, a method of synchronizing a radio device with aradio access node for radio communication is provided. The methodcomprises or triggers a step of receiving a configuration message fromthe radio access node, the configuration message being indicative of asynchronization signal configuration for a configurable synchronizationsignal. The method further comprises or triggers a step of receiving theconfigurable synchronization signal from the radio access node inaccordance with the synchronization signal configuration. The methodfurther comprises or triggers a step of communicating one or moredecodable signals between the radio access node and the radio deviceusing radio resources in accordance with the configurablesynchronization signal.

The other aspect of the technique may be implemented at the radiodevice.

The technique according to the other aspect may comprise any feature orany step disclosed in the context of the one aspect, or a feature or astep corresponding to the one aspect.

In any aspect, the radio access node (or briefly: node) may be a basestation or a cell of a network, e.g., a radio access network (RAN). Thenetwork may comprise the RAN and a core network (CN) connected to theRAN. Alternatively, or in addition, the radio access node or the RAN maybe connected to the Internet, e.g., via a gateway server. The radioaccess node may encompass any station that is configured to provideradio access to the radio device. The technique may be implemented atthe node in relation to a plurality of the radio devices. For example,multiple radio devices may camp on the cell or may be in a connecteddiscontinuous reception (DRX) mode with the radio access node.

The radio device may be configured for peer-to-peer communication, e.g.,on a sidelink to another radio device under the synchronization definedby (and optionally radio resource scheduling by) the radio access node.Alternatively or in addition, the radio device may be configured foraccessing the radio access node and/or the RAN. The communicating stepmay comprise an uplink (UL) to the radio access node and/or a downlink(DL) from the radio access node. The radio device may be a UE, a mobileor portable station (STA, e.g. a Wi-Fi STA), a device for IoT,particularly NB-IoT, MTC, eMTC or a combination thereof. Examples forthe UE and the mobile station include a mobile phone and a tabletcomputer. Examples for the portable station include a laptop computerand a television set. Examples for the MTC or eMTC device includerobots, sensors and/or actuators, e.g., in manufacturing and automotivecommunication. Examples for the NB-IoT device include sensors forsecurity systems and home automation. The radio device may beimplemented in household appliances and consumer electronics. Examplesfor the combination include a self-driving vehicle, a doorintercommunication system and an automated teller machine.

Examples for the radio access node may include a 3G base station or NodeB, 4G base station or eNodeB, a 5G base station or gNodeB, an accesspoint (e.g., a Wi-Fi access point) and a network controller (e.g.,according to Bluetooth, ZigBee or Z-Wave).

The RAN may be implemented according to the Global System for MobileCommunications (GSM), the Universal Mobile Telecommunications System(UMTS), Long Term Evolution (LTE) and/or New Radio (NR).

Each aspect of the technique may be implemented (e.g., partly orcompletely) on a Physical Layer (PHY) of a protocol stack for the radiocommunication. The technique may be supported or controlled by a MediumAccess Control (MAC) layer, a Radio Link Control (RLC) layer and/or aRadio Resource Control (RRC) layer of the protocol stack for the radiocommunication between the radio access node and the radio device.

As to another aspect, a computer program product is provided. Thecomputer program product comprises program code portions for performingany one of the steps of the method aspects disclosed herein when thecomputer program product is executed by one or more computing devices.The computer program product may be stored on a computer-readablerecording medium. The computer program product may also be provided fordownload via a data network, e.g., via the RAN, via the Internet,through the radio access node and/or through the radio device.Alternatively or in addition, any of the method aspects may be encodedin a Field-Programmable Gate Array (FPGA) and/or an Application-SpecificIntegrated Circuit (ASIC), or the functionality may be provided fordownload by means of a hardware description language.

As to one device aspect, a device for providing synchronization with aradio access node for radio communication to one or more radio devicesis provided. The device is configured to perform the one method aspect.

As to another device aspect, a device for synchronizing a radio devicewith a radio access node for radio communication is provided. The deviceis configured to perform the other method aspect.

As to a still further aspect, a device for providing synchronizationwith a radio access node for radio communication to one or more radiodevices is provided. The device comprises at least one processor and amemory. Said memory comprises instructions executable by said at leastone processor whereby the device is operative to transmit aconfiguration message to at least one of the radio devices, theconfiguration message being indicative of a synchronization signalconfiguration for a configurable synchronization signal; to transmit theconfigurable synchronization signal to the at least one radio device inaccordance with the synchronization signal configuration; and tocommunicate one or more decodable signals between the radio access nodeand the at least one radio device using radio resources in accordancewith the configurable synchronization signal.

As to a still further aspect, a device for synchronizing a radio devicewith a radio access node for radio communication is provided. The devicecomprises at least one processor and a memory. Said memory comprisesinstructions executable by said at least one processor whereby thedevice is operative to receive a configuration message from the radioaccess node, the configuration message being indicative of asynchronization signal configuration for a configurable synchronizationsignal; to receive the configurable synchronization signal from theradio access node in accordance with the synchronization signalconfiguration; and to communicate one or more decodable signals betweenthe radio access node and the radio device using radio resources inaccordance with the configurable synchronization signal.

As to a still further aspect, a device providing synchronization with aradio access node for radio communication to one or more radio devicesis provided. The device may comprise one or more modules for performingthe one method aspect. Alternatively or in addition, the devicecomprises a configuration transmission module for transmitting aconfiguration message to at least one of the radio devices, theconfiguration message being indicative of a synchronization signalconfiguration for a configurable synchronization signal. The devicefurther comprises a synchronization signal transmission module fortransmitting the configurable synchronization signal to the at least oneradio device in accordance with the synchronization signalconfiguration. The device further comprises a communication module forcommunicating one or more decodable signals between the radio accessnode and the at least one radio device using radio resources inaccordance with the configurable synchronization signal.

As to a still further aspect, a device for synchronizing a radio devicewith a radio access node for radio communication is provided. The devicemay comprise one or more modules for performing the other method aspect.Alternatively or in addition, the device comprises a configurationreception module for receiving a configuration message from the radioaccess node, the configuration message being indicative of asynchronization signal configuration for a configurable synchronizationsignal. The device further comprises a synchronization signal receptionmodule for receiving the configurable synchronization signal from theradio access node in accordance with the synchronization signalconfiguration. The device further comprises a communication module forcommunicating one or more decodable signals between the radio accessnode and the radio device using radio resources in accordance with theconfigurable synchronization signal.

Any one of the devices (or any node or station for embodying thetechnique) may further include any feature disclosed in the context ofthe corresponding one of the method aspects. Particularly, any one ofthe units and modules, or a dedicated unit or module, may be configuredto perform or trigger one or more of the steps of any one of the methodaspects.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of embodiments of the technique are described withreference to the enclosed drawings, wherein:

FIG. 1 shows a schematic block diagram of a device for providingsynchronization with a radio access node for radio communication to oneor more radio devices;

FIG. 2 shows a schematic block diagram of a device for synchronizing aradio device with a radio access node for radio communication;

FIG. 3 shows a flowchart for a method of providing synchronization witha radio access node for radio communication to one or more radiodevices, which is implementable by the device of FIG. 1;

FIG. 4 shows a flowchart for a method of synchronizing a radio devicewith a radio access node for radio communication, which is implementableby the device of FIG. 2;

FIG. 5 shows a schematic signaling diagram resulting from embodiments ofthe devices of FIGS. 1 and 2 in radio communication according to themethods of FIGS. 3 and 4, respectively;

FIGS. 6A, 6B and 6C schematically illustrates parameters of asynchronization signal configurations, which are applicable toembodiments of the devices of FIGS. 1 and 2 or implementations of themethods of FIGS. 3 and 4;

FIG. 7 schematically illustrates further parameters of a configuration,which is applicable to embodiments of the devices of FIGS. 1 and 2 orimplementations of the methods of FIGS. 3 and 4;

FIG. 8 shows a schematic block diagram of an embodiment of the device ofFIG. 1,

FIG. 9 shows a schematic block diagram of an embodiment of the device ofFIG. 2; and

FIG. 10 shows a schematic block diagram of a network comprisingembodiments of the devices of FIGS. 1 and 2.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and notlimitation, specific details are set forth, such as a specific networkenvironment in order to provide a thorough understanding of thetechnique disclosed herein. It will be apparent to one skilled in theart that the technique may be practiced in other embodiments that departfrom these specific details. Moreover, while the following embodimentsare primarily described for a 3GPP LTE implementation within theframework for machine-type communication, it is readily apparent thatthe technique described herein may also be implemented in any otherradio network, including NB-IoT or other modes of operation within 3GPPLTE or a successor thereof, 5G New Radio (NR), Wireless Local AreaNetwork (WLAN) according to the standard family IEEE 802.11, Bluetoothaccording to the Bluetooth Special Interest Group (SIG), particularlyBluetooth Low Energy and Bluetooth broadcasting, and/or ZigBee based onIEEE 802.15.4.

Moreover, those skilled in the art will appreciate that the functions,steps, units and modules explained herein may be implemented usingsoftware functioning in conjunction with a programmed microprocessor, anApplication Specific Integrated Circuit (ASIC), a Field ProgrammableGate Array (FPGA), a Digital Signal Processor (DSP) or a general purposecomputer, e.g., including an Advanced RISC Machine (ARM). It will alsobe appreciated that, while the following embodiments are primarilydescribed in context with methods and devices, the invention may also beembodied in a computer program product as well as in a system comprisingat least one computer processor and memory coupled to the at least oneprocessor, wherein the memory is encoded with one or more programs thatmay perform the functions and steps or implement the units and modulesdisclosed herein.

FIG. 1 schematically illustrates a block diagram of a device forproviding synchronization with a radio access node for radiocommunication to one or more radio devices. The device is genericallyreferred to by reference sign 100.

The device 100 comprises a configuration transmission module 102 thattransmits a configuration message to at least one of the radio devices.The configuration message is indicative of a synchronization signalconfiguration for a configurable synchronization signal. The device 100further comprises a synchronization signal transmission module 104 thattransmits the configurable synchronization signal to the at least oneradio device in accordance with the synchronization signalconfiguration. The device 100 further comprises a communication module106 that communicates (e.g., receives and/or transmits) one or moredecodable signals between the radio access node and the at least oneradio device. The communication uses radio resources in accordance withthe configurable synchronization signal.

The device 100 may be connected to and/or part of the radio access nodeor a RAN comprising the radio access node. The device 100 may beembodied by or at the radio access node of the RAN, other nodesconnected to the RAN for controlling the radio access node or acombination thereof. The device 100 may be spatially separated from theradio device.

Any of the modules of the device 100 may be implemented by unitsconfigured to provide the corresponding functionality.

FIG. 2 schematically illustrates a block diagram of a device forsynchronizing a radio device with a radio access node for radiocommunication. The device is generically referred to by reference sign200.

The device 200 comprises a configuration reception module 202 thatreceives a configuration message from the radio access node. Theconfiguration message is indicative of a synchronization signalconfiguration for a configurable synchronization signal. The device 200further comprises a synchronization signal reception module 204 thatreceives the configurable synchronization signal from the radio accessnode in accordance with the synchronization signal configuration. Thedevice 200 further comprises a communication module 204 thatcommunicates (e.g., receives and/or transmits) one or more decodablesignals between the radio access node and the radio device using radioresources in accordance with the configurable synchronization signal.

The device 200 may be connected to and/or part of the radio device. Thedevice 200 may be embodied by or at the radio device. The device 200 maybe spatially separated from the radio access node and/or the RAN.

Any of the modules of the device 200 may be implemented by unitsconfigured to provide the corresponding functionality.

The radio access node may also be referred to as a base station. Theradio access node may be configured to provide radio access to the oneor more radio devices. The radio access node may encompass a networkcontroller (e.g., a Wi-Fi access point) or a cellular radio access node(e.g. a 3G Node B, a 4G eNodeB or a 5G gNodeB). It may further encompassa user equipment (UE) or any other type of devices acting as a relaynode by providing the same or similar radio access functionality toother radio devices, e.g., as a cellular radio access node.

Alternatively or in addition, any one of the radio devices may include amobile or portable station or any radio device wirelessly connectable tothe RAN. Each radio device may be a user equipment (UE) and/or a devicefor machine-type communication (MTC), particularly enhances MTC (eMTC).Two or more radio devices may be configured to wirelessly connect toeach other, e.g., via 3GPP sidelinks and/or according to a schedulingprovided by the radio access node.

Each aspect, or a further aspect, of the technique may be implemented asa synchronization signal configuration specifying the usage (e.g.,whether the signal is actively used or deactivated, and/or parameters ofthe signal) of the configurable synchronization signal. Anyimplementation may be combined with a power-saving signal configurationspecifying the usage of the power-saving signal (e.g., whether thepower-saving signal is actively used or deactivated, and/or one or moreparameters of the power-saving signal). Alternatively or in addition,any implementation may be combined with a discontinuous receptionconfiguration (DRX configuration) specifying a discontinuous reception(DRX) performed by the radio device (e.g., whether the DRX is performedor deactivated, and/or one or more parameters of the DRX). Thesynchronization signal configuration and/or the power-saving signalconfiguration may be part of the DRX configuration. Herein, “DRX”encompasses enhanced DRX (eDRX). DRX may be performed in an idle mode,e.g., for paging, or in a connected mode of the radio device.Embodiments of the technique may be compatibility with section 7 of thedocument 3GPP TS 36.304, e.g., version 14.3.0.

The technique may be embodied by a configurable synchronization signalfor network resynchronization, e.g., not primarily intended for aninitial access. Alternatively or in addition, the configurablesynchronization signal may be configured to provide or support thesynchronization of the radio device prior to or in an active phase ofthe DRX for the radio communication. The active phases may comprise idlemode operations such as at least one of paging, verification of systeminformation and measurements for radio resource management (RRM).

The one or more radio devices may comprise one or more MTC devices. Dueto extremely varying demands and/or capabilities of MTC devices and/orextremely varying demands and/or capabilities of network deploymentssupporting MTC devices, the configurable synchronization signal isconfigurable by means of the configuration message. By means of thesynchronization signal configuration in the configuration message, autilization of resource elements (REs) for the configurablesynchronization signal or any other parameter of the configurablesynchronization signal can be variable, e.g., controlled by the RAN orthe CN.

The synchronization signal configuration, e.g., the length of theconfigurable synchronization signal, may dependent on a figure R_(max).The figure R_(max) is an indication of the maximum number of repetitionsthat is supported by the radio access node or a corresponding cell ofthe radio access node. The figure R_(max) may be applied for differentphysical channels, e.g., including the configurable synchronizationsignal. By making the synchronization signal configurable (and/orreconfigurable), it is possible to keep a network overhead low. Thenetwork overhead may be defined as the radio resources allocated tosignaling such as synchronization as compared to the available radioresources. The technique may be implemented to keep the network overheadlow in RANs or cells supporting radio devices under moderate SNR levels(or expected to operate under moderate SNR levels), while also allowingthe RAN or the cell to support radio devices under low SNR levels withthe associated higher overhead (e.g., greater number of repetition ascompared to the radio devices under moderate SNR levels). To this end,the synchronization signal configuration may vary with time and/or beradio device-specific. Further parameters of the synchronization signalconfiguration (e.g., depending on an expected load), may comprise aperiodicity of the configurable synchronization signal. Preferably, theconfigurable synchronization signal may be transmitted by the radioaccess node and received by the radio device prior to a periodiccommunication event, e.g., a paging occasion.

FIG. 3 shows a flowchart for a method 300 of providing synchronizationwith a radio access node for radio communication to one or more radiodevices. The method 300 comprises a step 302 of transmitting aconfiguration message to at least one of the radio devices. Theconfiguration message is indicative of a synchronization signalconfiguration for a configurable synchronization signal. In a step 304of the method 300, the configurable synchronization signal istransmitted to the at least one radio device in accordance with thesynchronization signal configuration. The method 300 further comprises astep 306 of communicating (e.g., receiving from and/or transmitting tothe radio access node) one or more decodable signals between the radioaccess node and the at least one radio device. The communication 306uses radio resources in accordance with the configurable synchronizationsignal, e.g., in accordance with the synchronization provided orsupported by the configurable synchronization signal when received atthe at least one radio device.

The method 300 may be performed by the device 100, e.g., at or using theradio access node. For example, the modules 102, 104 and 106 may performthe steps 302, 304 and 306, respectively.

The step of transmitting the configuration message and/or the step oftransmitting the configurable synchronization signal may be implementedby radio transmissions to the at least one radio device. The step ofcommunicating decodable signals may be implemented by a radiocommunication between the radio access node and the at least one radiodevice.

At least one of the configuration message and the configurablesynchronization signal may be transmitted from the radio access node.

The communication of the decodable signals may comprise an uplink radiocommunication to the radio access node and/or a downlink radiocommunication to the radio access node.

The radio resources in accordance with the configurable synchronizationsignal may encompass any radio resources in accordance or consistencywith the synchronization brought about by the configurablesynchronization signal. Particularly, the radio resources in accordancewith the configurable synchronization signal may encompass any radioresources that are defined in time and/or frequency (e.g., in timeframes or time-frequency grids) in accordance with or in consistencywith the synchronization defined by configurable synchronization signal.The radio resources may be defined in accordance with or in consistencywith the configurable synchronization signal.

The radio resources may also be in accordance with a predefined (e.g.,not configured or not configurable) synchronization signal, e.g., withthe PSS and/or the SSS. The synchronization provided by the PSS and/orthe SSS may be consistent with, or equal to, the synchronizationprovided by the configurable synchronization signal. The radio devicemay combine (e.g., average over) the predefined synchronization signaland the configurable synchronization signal, or multiple receptionsthereof.

The radio access node may be configured to provide radio access to theone or more radio devices, e.g., in one or more cells of the radioaccess node or of the RAN. For example, all or some of the radio devicesmay be in a coverage area of one of the cells. The radio access node maybe a base station of the RAN.

The radio access node may provide radio access to a plurality of theradio devices. In the idle mode, the corresponding radio device may campon the radio access node or a tracking area (TA) including the cell orthe radio access node.

The radio access node may transmit different configuration messages todisjoint groups of the radio devices. Different configuration messagesindicative of different synchronization signal configurations (and, forexample, different configurable synchronization signals according to therespective configuration messages) may be transmitted to the radiodevices belonging to different groups.

The groups and/or the one or more radio devices may be distinguished(e.g., for the purpose of transmitting the synchronization signalconfiguration) by at least one of a device category, a channel quality,a length of the configurable synchronization signal (e.g., including anumber of repetitions and/or a coding pattern) and a maximum number ofcontrol signal repetition.

The radio device may measure and/or report the channel quality to thenetwork (e.g., the RAN and/or the CN). The channel quality may berelated to, or represented by, a signal-to-noise ratio (SNR), a signalto noise and interference ratio (SNIR), a channel quality indicator(CQI), a reference signal received power (RSRP) and a reference signalreceived quality (RSRQ).

The channel quality, any one of the afore-mentioned quantities (e.g.,SNR, SNIR, CQI, RSRP and RSRQ) and/or quantities for radio resourcemanagement (RRM) or Radio Link Monitoring (RLM) may be based on one ormore measurements performed by the radio device. These measurements may,for example, be performed on the actual configurable synchronizationsignal (e.g., the configurable synchronization signal as received and/ordetected at the radio device) and/or any other auxiliary channel orauxiliary signal, such as, for example, but not limited to,Cell-specific Reference Signals (CRS). The auxiliary channel or signalis transmitted on radio resources that the radio device is able todetermine in accordance with the configurable synchronization signal.For example, the channel quality, or any one of the afore-mentionedquantities, may depend on and/or may be a measure for the accuracy ofthe synchronization provided or supported by the configurablesynchronization signal to the radio device.

For example, in the M2M domain, several different use cases areimaginable. One kind of network or one group of radio devices may beassociated with (e.g., expected or profiled to support) extremely lowSNRs, e.g., a maximum coupling loss (MCL) of 164 dB. Another kind ofnetwork or another group of radio devices may be associated with (e.g.,expected or profiled to support) devices with extremely long pagingintervals, up to several hours. This implies that the requirements on aresynchronization signal will differ significantly, due to the differentnetwork profiles or group profiles. The profiles associated with each ofthe radio devices may be based on the reports. The profiles may bestored in a radio device context associated with the corresponding radiodevice, e.g., at a mobility management entity (MME) of the CN. The onesynchronization signal configuration for the synchronization signal thatis preferred in the one kind of network or the one group of radiodevices may be adverse in the other kind of network or the other groupof radio devices.

Alternatively or in addition, at least one of the configuration message,the synchronization signal configuration and the configurablesynchronization signal may be cell-specific. For example, differentsynchronization signal configurations may be transmitted in differentcells of the RAN (e.g., different cells of the same radio access node).Any configuration message indicative of a cell-specific synchronizationsignal configuration may be advantageously transmitted as a broadcastmessage, e.g., as system information.

Alternatively or in addition, at least one of the configuration message,the synchronization signal configuration and the configurablesynchronization signal is radio device-specific. At least one of theconfiguration message, the synchronization signal configuration and theconfigurable synchronization signal may depend on a report received fromthe radio device, a device category, a quality of service (QoS)requirement of the radio device and a QoS class indicator (QCI) of theradio device. Any configuration message indicative of a radiodevice-specific synchronization signal configuration may beadvantageously transmitted as a dedicated radio resource control (RRC)signaling message (without precluding alternative implementation).

For the at least one radio device, the configurable synchronizationsignal may provide or support the synchronization with the radio accessnode. The synchronization of the at least one radio device may beexclusively based on the configurable synchronization signal.Optionally, the synchronization of the at least one radio device may besupported by the configurable synchronization signal. Supporting thesynchronization by the configurable synchronization signal may encompassreducing the time for completing the synchronization (as compared tocompleting the synchronization exclusively based on predefinedsynchronization signals) and/or improving an accuracy of thesynchronization (as compared to completing the synchronizationexclusively based on predefined synchronization signals).

The configurable synchronization signal may provide or support at leastone of a timing synchronization with the radio access node, a frequencysynchronization with the radio access node, a phase synchronization withthe radio access node and a channel estimate for a radio channel to orfrom the radio access node. The timing synchronization may enable theradio device to reduce or eliminate a time shift relative to the radioaccess node. The frequency synchronization may enable the radio deviceto reduce or eliminate a frequency shift relative to the radio accessnode. The phase synchronization and/or the channel estimate may enablethe radio device to reduce or eliminate a phase shift and/or anattenuation factor relative to the radio access node.

The configurable synchronization signal may provide or support thesynchronization for communicating the one or more decodable signals onthe radio resources. The radio resources may be structured in at leastone of time frames, time slots, subframes, transmission time intervals(TTIs), subcarriers and resource blocks (RBs).

The configurable synchronization signal may provide or support adownlink synchronization. The configurable synchronization signal mayprovide or support the synchronization with the radio access node forthe communication in a downlink from the radio access node to the atleast one radio device.

The communicating step may include receiving the one or more decodablesignals comprising a power-saving signal. The power-saving signal may beindicative of an instruction for operating a receiver at the radiodevice. The power-saving signal may comprise a wake-up signal (WUS). TheWUS may be indicative of an instruction for enabling the receiver, e.g.,at a later point in time, such as for reception of further channels orsignals. According to the WUS, the at least one radio device may enableits receiver for receiving the decodable signals in the communication onthe radio resources. The radio resources may be defined within a radioresource grid for REs in time and/or frequency in accordance with theDRX configuration (e.g., as a transmission opportunity or idle modepaging). The grid of REs may be defined time and/or frequency inaccordance with the synchronization provided or supported by theconfigurable synchronization signal. Alternatively and in addition, thepower-saving signal may comprise a go-to-sleep signal (GTS). The GTS maybe indicative of disabling the receiver, e.g., until the next time(e.g., according to the periodicity) for at least one ofresynchronization, reception or transmission.

The configuration message, or a further configuration messagetransmitted to at least one of the radio devices, may be indicative of apower-saving signal configuration for the power-saving signal. Thepower-saving signal may be selectively transmitted by the radio accessnode depending on the power-saving signal configuration. Thepower-saving signal configuration may be selectively expected by theradio device depending on the power-saving signal configuration, e.g.,by selectively enabling its receiver for receiving the power-savingsignal. The network, e.g., the RAN or the CN, may change thepower-saving signal configuration to activate or deactivate the usage ofthe power-saving signal, e.g., depending on whether or not,respectively, the power-saving signal reduces power consumption at thecorresponding radio device. Alternatively or in addition, the network,e.g., the RAN or the CN, may change the power-saving signalconfiguration to activate or deactivate the usage of the power-savingsignal, e.g., depending on whether or not, respectively, the networkoverhead is (e.g., on average) reduced.

The configuration message, or a further configuration messagetransmitted to at least one of the radio devices, may be indicative ofthe DRX configuration for a DRX operation of the at least one radiodevice or another one of the radio devices.

The radio device may be in an idle mode or a connected mode with theradio access node, e.g., according to a radio resource control (RRC)layer of a protocol stack for the radio communication.

Herein, “DRX” may encompass extended DRX (eDRX), e.g., according to thedocument 3GPP TS 36.304, version 13.3.0 (or later). The DRXconfiguration may be specific for and/or dedicated to the radio device.Alternatively or in addition, the DRX configuration may be specific forand/or dedicated to a group of radio devices, the radio access node or acell of the RAN.

The radio device may be in a sleep mode (e.g., as an inactive phase ofthe DRX) relative to the radio access node prior to the step oftransmitting the configurable synchronization signal. Alternatively orin addition, the radio device may be configured for performing idle modepaging (e.g., as an active phase of the DRX), e.g., while camped on theradio access node or the cell. The idle mode paging may also be referredto as paging in idle mode, DRX in idle mode or idle mode DRX.

The one or more decodable signals may comprise at least one of controldata and user data, e.g., from the radio access node. Examples for thecontrol data include a scheduling assignment and a scheduling grant. Theone or more decodable signals may comprise a paging message from orforwarded by the radio access node. The paging message may be an examplefor user data (e.g., comprising text of a short message service, SMS) orcontrol data (e.g., for updated system information).

The step of communicating may include broadcasting the one or moredecodable signals comprising system information. The system informationmay be broadcasted in a master information block (MIB) and/or one ormore system information blocks (SIBs).

The at least one radio device may read the broadcasted systeminformation, e.g., on a physical broadcast channel (PBCH) for the MIBand/or a physical downlink control channel (PDCCH) and a physicaldownlink shared channel (PDSCH) for the SIBs. The broadcasted systeminformation may be updated relative to a previously broadcasted systeminformation.

The one or more decodable signals may be communicated in an uplinkdirection from the at least one radio device to the radio access node.For example, the step of communicating the one or more decodable signalsmay comprise receiving a random access (RA) preamble from the at leastone radio device at the radio access node.

The radio resources in accordance with the configurable synchronizationsignal may comprise a physical random access channel (PRACH). A specificPRACH may be defined for NB-IoT or MTC. The method may further comprisetransmitting a random access response (RAR). The RAR may be indicativeof a timing advance (TA) providing uplink synchronization with the radioaccess node to the at least one radio device.

The configuration message and/or the synchronization signalconfiguration may be indicative of a physical structure of theconfigurable synchronization signal. The configuration message may beindicative of an allocation of radio resources for the configurablesynchronization signal. The physical structure may define resourceelements (REs) in at least one of time (e.g., in terms of TTIs or OFDMsymbols), frequency (e.g., in terms of subcarriers) and space (e.g., interms of spatial streams of a multiple-input multiple-output channel)for the configurable synchronization signal.

The configuration message may be indicative of a periodicity oftransmitting the configurable synchronization signal. Alternatively orin addition, the configuration message may be indicative of a length ofthe configurable synchronization signal in the time domain. Theconfiguration message may be indicative of a number of repetitions ofthe configurable synchronization signal. The configuration message maybe indicative of a gap between the repetitions. Repetitions of theconfigurable synchronization signal may be arranged according to anaperiodic coding pattern.

A coding pattern (e.g., for a long configurable synchronization signal)may be structured to detect (e.g., at the radio device) the configurablesynchronization signal based on receiving a portion (e.g., within thecoding pattern) of the configurable synchronization signal.Alternatively or in addition, the coding pattern may be structured(e.g., aperiodic) to determine (e.g., at the radio device) a beginning(or another reference point in time) of the configurable synchronizationsignal based on receiving a portion (e.g., within the coding pattern) ofthe configurable synchronization signal. As soon as the radio device hasdetermined the beginning (or the other reference point in time) of theconfigurable synchronization signal by virtue of the coding pattern, theradio device may cease receiving, detecting or decoding a reminder ofthe configurable synchronization signal. The synchronization signalconfiguration may be indicative of the coding pattern.

The configurable synchronization signal may be transmitted according toa coding pattern at one or multiple transmission occasions. Sequences orsignals transmitted within each transmission occasion and/or indifferent transmission occasions may be identical or comprisecombinations of different sequences or signals.

The configuration message may be indicative of a bandwidth of theconfigurable synchronization signal in the frequency domain. Thebandwidth may depend on the radio device category or the capability ofthe radio device.

The configurable synchronization signal may be a physical signal. Asequence of complex-valued symbols may be encoded in the configurablesynchronization signal. The sequence may yield a constant amplitude orconstant-power envelope, e.g., of the configurable synchronizationsignal. Alternatively or in addition, an autocorrelation of the sequencemay vanishing for any (e.g., integer) relative shift of the symbols ormay be inversely proportional to the length of the sequence. Thesequence may comprise at least one of a Zadoff-Chu sequence and amaximum length sequence (MLS) or m-sequence.

The configurable synchronization signal may be transmitted in additionto at least one predefined synchronization signal transmitted by theradio access node. The configurable synchronization signal may depend onthe synchronization signal configuration. For example, the predefinedsynchronization signal may be cell-specific. Alternatively or inaddition, the predefined signal may be independent of a (e.g.,cell-specific or radio device-specific) configuration. The predefinedsignal may be specified upon deployment of the radio access node. Thepredefined signal may comprise a primary synchronization signal (PSS)and/or a secondary synchronizing signals (SSS). The configurablesynchronization signals may be transmitted in addition to at least oneof a PSS and a SSS transmitted by the radio access node.

A synchronization with the radio access node upon an initial access ofthe at least one radio device may be based (e.g., exclusively) on atleast one predefined synchronization signal. The configuration messagemay be transmitted upon or after the initial access.

The configurable synchronization signal may be temporally aligned toradio communication events in the radio communication between the radioaccess node and the at least one radio device. The events may bescheduled, pre-scheduled, configured and/or semi-persistently scheduledby the radio access node. The events may be periodic. The events mayinclude at least one of a paging occasions (e.g., according to the DRXconfiguration) and the transmission of the power-saving signal (e.g.,according to the power-saving signal configuration).

The configurable synchronization signal may be transmitted temporallyahead of the event. At least one configurable synchronization signal maybe transmitted temporally ahead of each of the event. The periodicity ofthe events may correspond to the periodicity of the configurablesynchronization signals.

The configurable synchronization signal may be indicative of a change insystem information. The change in the system information may be anexample of the event. The system information may be broadcasted by theradio access node, e.g., for the cell. The system information may bebroadcasted in a master information block (MIB) and/or one or moresystem information blocks (SIBs) of the radio access node or a cellassociated with the radio access node.

The configuration message may comprise a reference to an entry in a bookof synchronization signal configurations. The reference may be an index.The book may be a table or a data structure representing the table. Theentry may be a row of the table. The book of configurablesynchronization signals may be stored at the radio access node and/orthe at least one radio device. The book may be predefined by a standardand/or exchanged between the radio access node and the radio device uponthe initial access. Each entry may comprise a set of parameters definingthe structure of the associated configurable synchronization signal.

FIG. 4 shows a flowchart for a method 400 of synchronizing a radiodevice with a radio access node for radio communication. The method 400comprises a step 402 of receiving a configuration message from the radioaccess node. The configuration message is indicative of asynchronization signal configuration for a configurable synchronizationsignal. The method 400 further comprises a step 404 of receiving theconfigurable synchronization signal from the radio access node inaccordance with the synchronization signal configuration. In a step 406,one or more decodable signals are communicated between the radio accessnode and the radio device (e.g., received from and/or transmitted to theradio access node) using radio resources in accordance with theconfigurable synchronization signal.

The method 400 may be performed by the device 200, e.g., at or using theradio device. For example, the modules 202, 204 and 206 may perform thesteps 402, 404 and 406, respectively.

Any embodiment of the method 400 may further comprise any feature orstep disclosed in the context of the method 300, as well as features orsteps that correspond to those of the method 300 as the devices 100 and200 are in the radio communication.

Multiple aspects of the technique can be embodied. These aspects includesystem aspects, network node aspects related to the radio access nodeand network device aspects related to one of the radio devices andsignal aspects related to a signal structure for the configurationmessage and a signal structure for the configurable synchronizationsignal.

According to a system aspect, the technique is related to an adaptablesystem for wireless communications 306 and 406, which is adaptable bymeans of the configuration message such that the system may provide aconfigurable resynchronization signal, e.g., according to a specifictransmission pattern.

The system comprises the radio access node and one or more radiodevices. The radio access node may be any wireless network node (e.g.,an eNB and/or gNB) that determines the synchronization signalconfiguration and configures the radio devices accordingly in the step302, in addition to transmitting the configurable synchronization signalin the step 304. Each radio device, which may also be referred to as awireless device or UE, is configured to detect the configurablesynchronization signal according to the synchronization signalconfiguration received in the step 402, e.g., a specific configuration,and then to attempt detecting the configurable synchronization signal inthe step 404 according to the synchronization signal configuration.

The synchronization signal configuration may specify the transmissionpattern. For example, the synchronization signal configuration comprisesat least one of following parameters. A first parameter is the number ofrepetitions or segments of the configurable synchronization signal, orthe sequence encoded therein, used in each transmission occasion. Asecond parameter is the presence of gaps (i.e., with or without gaps) orduration (i.e., length of the gap) between the repetitions or thesegments. A third parameter is the length of the configurablesynchronization signal, or the sequence encoded therein. A fourthparameter is the periodicity of transmission occasions of theconfigurable synchronization signals, or the sequences encoded therein.A fifth parameter is the timing offset for each transmission occasion,e.g., relative to each of the transmission opportunities defined by theDRX configuration or any other communication event. The timing offsetmay further represent a value for the start of each transmissionoccasion within the configured periodicity, e.g., represented as a framenumber, subframe number, TTI, etc. A sixth parameter comprises afrequency location and the bandwidth, e.g., the number of frequencybands. Each of the frequency bands may consist of a contiguous set ofRBs. Each of the frequency bands may be associated with the frequencylocation and/or the bandwidth used for each transmission occasion.Without limitation, each frequency band may correspond to a partition ofa system bandwidth. A radio device of a particular type or radio devicecategory may be scheduled according to its type or category. Forexample, the radio resources allocated for an NB-IoT radio device maycomprise one physical RB (PRB), the radio resources allocated for aCat-M1 radio device may be one narrow band, i.e., 6 PRBs, the radioresources allocated for a Cat-M2 radio device may be one wide band,i.e., 24 PRBs.

The network, its RAN or its radio access node may configure one or moretransmission patterns to cater for different device types (e.g., definedin terms of the radio device categories) and/or coverage levels (e.g.,defined in terms of the MCL). For example, for the same coverage target,devices capable of receiving wider bandwidth signal (e.g., Cat M-2devices) may be configured with a transmission pattern with a smallnumber of repetitions and large bandwidth, while devices capable ofreceiving narrower bandwidth signal (e.g., Cat M-1 devices) may beconfigured with a transmission pattern with large number of repetitionsand narrower bandwidth. This can allow the radio device, which iscapable of receiving the wider bandwidth signal, to finish theresynchronization more quickly.

The time domain parameters of the transmission pattern may be expressedin any suitable time unit or combination of time units, such as OFDMsymbols, subframes, radio frames, milliseconds, TTIs, etc. In an exampleembodiment, these parameters are configured with fixed values, but theymay also vary according to ways known to both the radio access node andthe radio device. The configurable synchronization signals, or theunderling sequences, used within each transmission occasion and/or indifferent transmission occasions may be identical or comprisecombinations of different sequences or signals. The repetitions orcombinations may be transmitted with gaps or without gaps.

Similarly, the frequency location and the bandwidth may be expressed inany suitable frequency unit, such as subcarriers, REs, resource blocks,Hertz (Hz), etc. The parameters for the frequency location and/or thebandwidth may be configured to fixed values that are identical for alltransmission occasions, or they employ frequency hopping within atransmission occasion and/or between transmission occasions.

Furthermore, the configurable synchronization signals, or the underlingsequences, may include (e.g., represent or be encoded with) additionalinformation, e.g., by altering the configurable synchronization signals,or the underling sequences. The included information may comprise atleast one of the following pieces of information. A first information isa Cell ID, e.g. the Cell ID also provided through the PSS and the SSS,or some other identity, for distinguishing between signals fromdifferent cells. A second information is timing information, e.g.,information reflecting a system frame number (SFN), such as a subset ofa bit sequence representing the SFN. This may be used to achieve timingresolution after a long timing drift in the radio device (e.g., after along period of the sleeping mode). A third information is currency orvalidity of system information (SI) and/or a value tag or hash value,e.g. one or more bits indicating whether the SI has been updated duringthe last X time units, wherein X may be a configured value or preset ina standardization document. The radio device may use third informationto determine that it may read system information less frequently inorder to save power. A fourth information is any information related toaccess barring (AB), e.g. similar or equivalent to a flag indicativethat AB is enabled (e.g., similar to an existing flag in the MIB forNB-IoT, such as MIB-NB). If the fourth information is provided in theconfigurable synchronization signal, the radio device may determine inthe step 404 that it does not need not read the MIB and/or the SIBs forconfirmation each time before accessing the radio access node or thecorresponding cell.

In one implementation compatible with an embodiment, the sequencesunderlying the configurable synchronization signal (e.g., the sequencesmentioned above) may be based on Zadoff-Chu sequences. In anotherimplementation compatible with an embodiment, the sequences may be basedon MLSs or m-sequences. Various modifications of such sequences are alsopossible, which are well known in the art.

In case the additional information is provided in the configurablesynchronization signal, the additional information may be conveyed byaltering a sequence index such that each sequence index implies acertain piece of information. Alternatively, the information may beconveyed by applying additional scrambling codes, masking, and/or covercodes. These may be applied identically to or differently to eachrepetition or combination of the configurable synchronization signals orthe underling sequences. The number of bits and/or encoding used torepresent each type of information can be fixed or variable, for exampleconfigured in order to reflect requirements in the current deploymentscenario.

In order to improve detection performance, the configurablesynchronization signals, or the underling sequences, with a certainsequence length or certain number of repetitions are transmitted in acontiguous resource blocks (RB) in order to reduce a receive duration atthe radio device. This does not exclude that within a RB, not allresource elements (RE) may be allocated to the sequence, e.g., due torestrictions in the transmission configuration. By way of example,downlink control information (DCI) configuration and reference signaltransmissions may be examples of such restrictions. It may, however, bethe case that the same or a predetermined RB utilization is usedthroughout all RBs.

The synchronization signal configuration of the resynchronizationsignals may be different in different cells. This may concern any of theabove-mentioned parameters in time and/or frequency domain. Tofacilitate coordination of the resynchronization signals between thecells, specific signaling may be introduced between radio access nodes(e.g., between the base stations), e.g. via the X2 interface in an LTEimplementation of the network. Additionally or alternatively, specificsignaling may be introduced between the RAN (e.g., the radio access nodeas one of the base stations) and the CN (e.g., one of the core networknodes), e.g. via the S1 interface between an eNB and an MME within thesame tracking area (TA) in an LTE implementation of the network.

In addition, the at least one radio device or any one of the radiodevices may receive information about configurable synchronizationsignals (e.g., resynchronization signals) present (e.g., configured) inneighboring cells, e.g. via RRC signaling. This information may be usedby the radio device, e.g., to look for alternative configurablesynchronization signals (e.g., resynchronization signals) and/or toapply interference cancellation, e.g., if the configurablesynchronization signals overlap at least partially in time andfrequency.

According to a base station aspect related to the access node, thetechnique is realized as the method 300 in a wireless network node (NN)for transmitting configurable synchronization signals from a basestation (BS) to a radio device, within a wireless system. The method 300may further comprise (e.g., as sub-steps of the step 302) at least oneof the following steps: a step of determining a transmission pattern ofthe configurable synchronization signals and a step of allocating theconfigurable synchronization signal in time-frequency resources. In thestep 304, the configurable synchronization signal is transmitted.

The transmission pattern comprises at least one of a configurable numberof repetitions, alternatively a configurable sequence length, pertransmission occasion; and a configurable periodicity between twoconsecutive transmission occasions. Alternatively or in addition, thetransmission pattern may depend on one or more of the above-mentionedparameters (e.g., those further configuration parameters discussed inrelation to the system aspects).

In an implementation of the step of determining the transmissionpattern, the NN configures the one or more radio devices connected tothe BS to detect the determined transmission pattern according to thestep 302. In the step 302, the synchronization signal configuration isperformed (i.e., the configuration message is transmitted), e.g., byMPDCCH messaging or System Information broadcast to the one or moreradio devices.

In one instance of the step 302, all radio devices in the cell orassociated to the radio access node are configured according to the samesynchronization signal configuration. In another instance of the step302 at least some of the radio devices are configured differently, suchthat, e.g., every 10th configurable synchronization signals is larger(e.g., longer in the time domain), thereby allowing for one or moreradio devices with lower SNRs to detect the different configurablesynchronization signal. Preferably, the remaining configurablesynchronization signals are transmitted with a smaller transmissionpattern (e.g., shorter in the time domain).

In any embodiment, the synchronization signal configuration may betransmitted in the step 302 by both broadcast signaling, such as systeminformation, multicast signaling or unicast signaling, such as dedicatedRRC signaling. An example of the SI broadcast is that a semi-staticsynchronization signal configuration is broadcasted in a specific SystemInformation Block (SIB) or added to an existing SIB. Any dynamic changeof the synchronization signal configuration may be subject to anexisting SI update procedure, that is, possible to update at thebroadcast control channel (BCCH) modification boundaries at the fastest.

An example of dedicated RRC signaling comprises using the configurablesynchronization signal for resynchronization with DRX or eDRX in theRRC_CONNECTED mode. The configurable synchronization signal may be radiodevice-specific and also transmitted selectively by the BS, e.g. onlywhen at least one radio device is in RRC_CONNECTED mode. Thus the systemoverhead is not unnecessarily increased.

In one embodiment, the synchronization signal transmission pattern isconfigured to be related to a paging periodicity, such that onetransmission occasion occurs just prior to possible paging occasionsand/or paging time windows depending on the DRX or eDRX cycle. Inanother embodiment, which is combinable with the one embodiment, thetransmission pattern may be configured such that one transmissionoccasion occurs just prior to a physical broadcast channel (PBCH)transmission. In yet another embodiment, which is combinable with theother embodiments, the transmission 304 may be related to a physicalrandom access channel (PRACH) periodicity. In a fourth embodiment, whichis combinable with any of aforementioned three other embodiments, thesynchronization signal may be mapped to the periodic TAU timer used forpower-saving mode (PSM). In a fifth embodiment, which is combinable withany of aforementioned four other embodiments, the configurablesynchronization signal is transmitted in the step 304 in the target cellupon handover. In a sixth embodiment, which is combinable with any ofaforementioned five other embodiments, the configurable synchronizationsignal is transmitted in the step 304 according to a predeterminedpattern used for radio link monitoring (RLM) and mobility measurements.In a seventh embodiment, which is combinable with any of aforementionedsix other embodiments, the synchronization signal is transmitted in thestep 304 upon SI update, i.e. at the start or just before the BCCHmodification period in which radio devices acquire the updated SIaccording to the step 306 subsequent to the modification period in whichthe radio devices are notified about the SI update.

Optionally, in any of the embodiments, the configurable synchronizationsignal is transmitted prior to any of the other signals (which areexamples of the events), possibly with a gap in-between allowing the atleast one radio device to perform post-processing, e.g., in order toproperly detect the configurable synchronization signal beforeadditional reception of the other signal according to the step 306, suchas paging or PBCH, or PRACH transmission according to the step 306.

According to a UE aspect, the technique may be implemented as the method400 of receiving, in the step 404, a configurable synchronizationsignal. The method 400 may further comprise at least one of the steps ofreceiving the synchronization signal configuration in the step 402; andattempting to detect the configurable synchronization signal in the step404 according to the received synchronization signal configuration.

The step 402 may comprise detecting the synchronization signalconfiguration, in turn, comprising at least one of the sub-steps:determining when the radio device needs to be synchronized orresynchronized (i.e., the in-synchronization time); determining anecessary synchronization accumulation time occurring prior to thein-synchronization time; and determining a wake-up time from thein-synchronization time and the synchronization accumulation time.Furthermore, the radio device may use information about thesynchronization signal configuration, periodicity and offset from othersignals and channels to determine the wake-up time.

The step of determining when the radio device needs to be synchronizedmay comprise, e.g., any occurrence of when the radio device has beenconfigured to monitor paging messages from the network, any occurrenceof when the radio device has been configured to perform measurementsrelated to, e.g., handover or other Radio Resource Management (RRM)procedures, or any occurrence of when the radio device intends to accessthe network, e.g., via a Random Access (RA) procedure.

The step of determining a necessary synchronization accumulation timemay comprise, e.g. knowledge or estimations in the radio device about aknown maximum time and/or a frequency drift since the last time theradio device was synchronized. This in turn may depend on the accuracyof a crystal oscillator that the radio device is basing its timing andfrequency reference on.

The radio device may further determine a necessary synchronizationaccumulation time based on knowledge or estimation of the SNR at whichthe radio device operates. One such estimation comprises reusing aprevious estimation of the SNR from the last time when the radio devicewas synchronized with the network and/or able to receive signals fromthe serving cell. If the radio device operates in a low SNR region, suchas below −15 dB, the radio device may need to receive and accumulatemore energy (e.g., multiple receptions 404) in order to successfullyresynchronize to the cell. This may correspond to receiving severalsubframes of the configurable synchronization signal. If the radiodevice operates in a higher SNR region, such as above 0 dB, the radiodevice may be able to resynchronize in much shorter time, e.g. usingonly a few OFDM symbols.

In some implementation, the radio device may decide based on such a SNRvalue (e.g., equal to or greater than 0 dB) to perform resynchronizationusing the predefined PSS and/or SSS sequences rather than using theconfigurable synchronization signal, for example if the radio devicedetermines that using the predefined synchronization signals is likelyto lead to less energy consumption.

In a further embodiment, the radio device may use the information aboutthe configurable synchronization signal being collocated with thepredefined synchronization signals (e.g., PSS and/or SSS) such that thepredefined synchronization signal and the configurable synchronizationsignal are combined in order to achieve synchronization. In that case,all three synchronization signals (PSS, SSS and configurablesynchronization signal) are correlated (e.g., convoluted in the timedomain) with respective synchronization sequences taking into accountindividual timing differences among them when combining. In that case, aradio device that failed to detect the synchronization by using theconfigurable synchronization signal may, by combining PSS and/or SSSsequences, still be able to achieve the synchronization without havingto wait for the next configurable synchronization signal, and possiblystill be able to receive any subsequent data that it planned to receive,e.g., before the next configurable synchronization signal is transmittedin the step 404.

In some embodiments, the necessary synchronization accumulation time maydepend on the further operations to be performed by the radio device,e.g., in the step 406. For example, if the radio device is configured tomonitor a possible paging indication from the network, and thisindication is provided by a dedicated wake-up signal for this purpose,the required synchronization accuracy for detecting this wake-up signalmay be different compared to, e.g., when the radio device needs toperform reception and decoding of another physical channel. Hence, thenecessary synchronization accumulation time may depend on thepower-saving signal configuration of such wake-up signal.

In some embodiments, the radio device may use the configurablesynchronization signal to obtain time and/or frequency synchronizationto a certain level of accuracy, e.g., followed by using another signalto further refine either or both of these estimates. In one suchembodiment, the UE uses a PBCH signal transmitted from a base stationoccurring shortly after the resynchronization signal for this purpose,before continuing with further reception and transmission of signals andchannels. In a further embodiment, the UE may use information about thereal time clock or a local oscillator in order to estimate a timingdrift that may have occurred from the last sync. Here the UE may alsocompensate for known drift, such that the estimated drift is minimized,thereby allowing for a minimized reception duration and minimized powerconsumption. The estimated drift may for example be based on an observeddrift in earlier resynchronization occasions.

The invention can be applied when the UE is configured in an active modesuch as RRC_CONNECTED in LTE. In some of these embodiments, the UE hasbeen configured with a long discontinuous reception (DRX) or enhancedDRX (eDRX) cycle such that the timing and/or frequency has drifted withan amount that is longer than a threshold, where the threshold indicatesa maximum drift that can be tolerated without having the need for moreaccurate synchronization before performing further reception ortransmission actions. In time domain, this threshold may correspond tothe cyclic prefix length, or a fraction thereof. In frequency domain,the threshold may correspond to for example a few tens to 100 Hz, forwhich reception of a control channels (such as MPDCCH), data channels(such PDSCH) or broadcast channels (such as PBCH) may be receivedwithout too much degradation.

The technique may further be applied when the radio device is configuredin an inactive mode such as RRC_IDLE in an LTE implementation or a 5Gimplementation. Even if the radio device is mostly inactive in thisstate, it is expected to wake up regularly to check, e.g., pagingmessages and/or perform measurements (as configured by the network) inthe step 406.

The technique may also be applied when the radio device is in a powersaving mode (PSM), such as the one defined for 3GPP LTE. E.g., comparedto DRX, the radio device is not attached to the RAN while in the PSM.The radio device needs to resynchronize to the RAN when returning fromthe PSM, e.g. in order to perform the random access (RA) procedure,optionally followed by a tracking area update (TAU), according to thestep 406.

FIG. 5 shows a schematic signaling diagram 500 for the radiocommunication between a radio access node embodiment 800 (e.g., an eNB)of the device 100 and a radio device embodiment 900 (e.g. a UE) of thedevice 200. Furthermore, a status 530 of the radio device 900 isindicated at the right-hand side of FIG. 5.

Implementations of the methods 300 and 400 may comprise further stepsin-between or substeps of the steps shown in FIG. 5. For example,confirmations or acknowledgments of received messages are omitted forclarity.

In a configuration stage 532, the UE 900 is being configured accordingto the step 402. The eNB 800 configures the UE 900 regarding theproperties (e.g., any one of above-mentioned parameters) of theconfigurable synchronization signal by transmitting the configurationmessage 510 according to the step 302. In further, optional steps, theUE 900 is also configured regarding a power-saving signal (e.g., awake-up signaling or WUS) in a power-saving signal configuration message512 and/or a DRX configuration message 514. The DRX configuration 514may be indicative of MPDCCH paging formats and paging configuration,including DRX cycles or eDRX cycles. In this configuration stage 532,the order of the messages may be irrelevant, since the UE 900 is not yetoperating according to any of the configurations 510, 512 and 514.

At the end of a sleep mode stage 534, when the UE 900 is operatingaccording to the above configurations 510, 512 and 514, the UE 900 wakesup from the sleep mode 534, presumably with a timing and/or frequencyerror sufficiently large for requiring network resynchronization. Afterwaking up, the UE 900 attempts to detect in the step 404 theconfigurable synchronization signal 520 for further operations accordingto the step 406. In the example shown in FIG. 5, the UE 900 isattempting to detect a power-saving signal 522, e.g., a wake-up signal(WUS). The wake-up signal 522 in this sense may comprise a signal thatis only transmitted when the UE 900 needs to perform further actions inthe step 406. Alternatively or in addition, the power-saving signal 522may be a periodically transmitted signal functioning as either a wake-upsignal or a go-to sleep signal in each instance depending on whether ornot data 524 or 526 is available at the eNB 800. That is, thepower-saving signal 522 differs in its information content. Otherpossibilities are to directly try to detect the control data 524, e.g.,a MPDCCH paging, e.g., in case WUS is not configured, i.e., thepower-saving signal 522 is deactivated according to the power-savingsignal configuration 512. If the power-saving signal 522 (e.g., the WUS522 in the stage 538) and/or the control data 526 (e.g., a schedulingassignment or paging message on the MPDCCH in the stage 540) indicatesthat the UE 900 receives user data 526, the UE 900 further receives theassigned radio resources, e.g., a PDSCH message carrying the user data526 in the stage 542 (which may include the actual paging message)and/or any further actions according to the communication step 406.Having finished all communication activities in the step 406, the UE 900falls back into the sleep mode 544 in order to preserve power, until itsnext activity.

The example described in FIG. 5 relates to the paging mechanism, butcorresponding signaling diagrams may be derived for any of the otherscenarios described herein. For example, if the communication actions inthe step 406 following the resynchronization in the step 404 aims atreceiving other signals, e.g., system information acquisition (i.e., MIBand/or one or more SIBs), the UE 900 receives on the PBCH and/orMPDCCH/PDSCH.

For NB-IoT, a specific NB-IoT PSS (NPSS) and/or a specific NB-IoT SSS(NSSS) is transmitted on an anchor carrier, e.g., according to 3GPPRelease 13. Moreover, in one alternative embodiment of the above, thesynchronization signal configuration 510 contains information aboutwhich carrier, optionally including non-anchor carriers, theconfigurable synchronization signal is to be received on in the step404.

The subframes used for the configurable synchronization signal 520 maybe indicated as invalid downlink (DL) subframes in a bitmap containingthis information such that Rel-13 and Rel-14 eMTC UEs 900 may notconsider these subframes as valid DL subframes for other purposes thanthe configurable synchronization signal 520. However, it is alsopossible that the eNB 800 coordinates different transmissions indifferent frequency regions via scheduling or configuration such that noRel-13 or Rel-14 eMTC UE 900 intends to use the particular time andfrequency resources occupied by the configurable synchronization signal520 for other purposes.

The configurable synchronization signal 520 according to the techniqueis preferably intended to be used for re-synchronization and not forinitial synchronization. For example, at initial acquisition, a UE 900would not know if or how it is configured or even supported in a cell ofthe eNB 800. Furthermore, some embodiments of the technique apply afixed (e.g., UE-specific) synchronization signal configuration 510(e.g., mapped to PBCH transmission as of above) is either hard-codedaccording to a specification or used in the entire network. In thiscase, the step 302 may be omitted.

While embodiments have been described herein from a system aspect, abase station aspect and/or a radio device aspect, the skilled personappreciates that the embodiments will have counterparts in the otheraspects, i.e., correspond features and/or corresponding steps, which arepart of the present disclosure. E.g., signals disclosed as transmittedby the radio access node 800 (e.g., a network node) in a certain fashionhave a counterpart in the radio device 900 (e.g., a UE) receiving thesame type of signal, and vice versa.

Moreover, the power-saving signal 514 may be selectively transmitted inthe step 406 depending on the DRX configuration 514 and/or thepower-saving signal configuration 512. The DRX configuration 514 and/orthe power-saving signal configuration 512 may specify that thepower-saving signal be used (e.g., that the WUS or the GTS be used)subject to the availability of data 524 and/or 526, or that thepower-saving signal 522 be not used (even if there is data 524 and/or526). In other words, the DRX configuration 514 and/or the power-savingsignal configuration 512 may specify whether or not reception of thepower-saving signal 522 is to be expected by the radio device 900, whichimplies a corresponding operation of the receiver at the radio device900. Alternatively or in addition, the DRX configuration 514 or thepower-saving signal configuration 512 may specify the power-savingsignal, e.g., as to a length in the time domain, a number ofrepetitions, a bandwidth in the frequency domain and a transmit power ofthe power saving signal.

The receiver may be enabled at the radio device 900, if the DRXconfiguration 514 or the power-saving signal configuration 512 specifiesthat the power-saving signal 522 be used. Enabling the receiver (e.g., areceiving unit and/or a decoding unit) may comprise supplying electricalpower to the receiver. The receiver may be disabled prior to the step ofselectively enabling the receiver.

The time and/or energy consumed for receiving the power-saving signal522 may be less than (e.g., a fraction of) the time and/or energynecessary for receiving the data 524 or 526. Disabling the receiver(e.g., the receiver unit) may comprise interrupting supply of electricalpower to (e.g., at least some parts of) the receiver.

The method 400 may further comprise a step of directly receiving fromthe radio access node 800 (e.g., on a radio resource according to theDRX configuration 514) the control data 524 and/or user data 526, if thepower-saving signal configuration 512 specifies that the power-savingsignal be not used.

FIGS. 6A, 6B and 6C schematically illustrate, in a time-frequency grid,examples of the synchronization signal configuration 600, e.g.,parameters of the transmission pattern, optionally including the codingpattern. Reference sign 602 indicates radio resources for transmissionoccasions for transmitting the configurable synchronization signal 520in each case.

The synchronization signal configuration 600 in the configurationmessage 510 for the configurable synchronization signal 520 may definethe transmission pattern, optionally including the coding pattern. Thesynchronization signal configuration 600 may further depend on theconfiguration of other physical signals or channels. One such signal mayfor example be a wake-up signal 522, intended to be used by the networkto indicate that one or more UEs 900 are being paged. In someembodiments, one or more of the above-mentioned configuration parametersof the configurable synchronization signal 520 may be related to one ormore configuration parameters of such a wake-up signal 522. For example,the DRX cycle length (e.g., a paging period) may define the periodicity608 in the synchronization signal configuration 600. A further optionalparameter of the synchronization signal configuration 600 is a timingoffset. A configured timing offset may correspond to a shift in time ofthe transmission pattern 602 compared to a nominal timing. Alternativelyor additionally, the synchronization signal configuration 600 may dependon the maximum number of repetitions configured in the network fordifferent signals or physical channels, e.g., the MPDCCH or PDSCH.

A base station profile (e.g., stored at the radio access node 800) maydetermine the synchronization signal configuration 600 of theconfigurable synchronization signal 520, e.g., as schematicallyillustrated in FIGS. 6A, 6B and 6C. This profile may depend on, e.g., adesired cell coverage (e.g., in terms of the MCL level) and/or arequirement for maximal latency (e.g., related to the QoS requirement)such that more radio resources 602 are allocated for the transmission304 of the configurable synchronization signal 520. E.g., a longersignal in the time domain, i.e., a greater length 604 as one of theconfiguration parameters, may be set in a cell requiring a highercoupling loss, as schematically illustrated in FIG. 6A.

Another property (e.g., radio condition or capability) that may affectthe synchronization signal configuration 600 is the paging periodicity608 of UEs 900 in the cell. UEs 900 with a higher paging period 608,which can imply or experience a greater timing deviation, may benefitfrom more frequently transmitted configurable synchronization signals510 on corresponding resources 602, as schematically illustrated in FIG.6B.

Both properties described with reference to the FIGS. 6A and 6B arecombinable, e.g., at the expense of a higher network overhead, which isschematically illustrated in FIG. 6C. It is also possible to vary theresource allocation in the frequency domain, such that a smaller orlarger part of the spectrum is covered by the radio resource 602 for theconfigurable synchronization signal 520 according to the bandwidth 606as a configuration parameter. Hence, a network may decide to target oneor the other or both of the above properties, e.g., with a correspondingvarying synchronization signal configuration 600. The combination of theconfiguration parameters allows the network to control the networkoverhead.

FIG. 7 schematically illustrates further parameters of thesynchronization signal configuration 600 and/or a DRX configuration 700carried in the DRX control message 514. As schematically illustrated inFIG. 7, for the use of faster synchronization before paging occasions(PO) 702, i.e. for DRX or eDRX in RRC_IDLE mode, in one embodiment theradio access node 800 (e.g., the BS) may broadcast the configurablesynchronization signal 520 in the corresponding radio resources 602 witha time offset prior to each subframe used for the paging in the cell.I.e., not only the subset used by a certain UE 900 receives in the step404 the configurable synchronization signal 520, since it is not knownto the BS 800 which of the UEs camp on the cell.

In some embodiments, the synchronization signal configuration 600 of theconfigurable synchronization signal 520 enables the UE 900 to achievecombining gains by receiving both the predefined synchronization signals(which may also be referred to as regular synchronization signals, e.g.,PSS and/or SSS) and the configurable synchronization signal 520. As anexample, for a Cat-M1 UE 900, this combining can be facilitated bymapping the configurable synchronization signal 520 to the same72-subcarrier region 602 in the center of the LTE system bandwidth alsoused for the regular LTE PSSs and LTE SSSs.

The radio resources 702 are transmission opportunities according to theDRX configuration 700. Depending on the power-saving signalconfiguration 512 (optionally as part of the DRX configuration message514), the power-saving signal 522 is selectively transmitted topreemptively inform the radio device 900 of whether or not the nexttransmission opportunity 702 is used, i.e., whether or not there will bea transmission of control data 524 or user data 526 for the radio device900 on the next radio resource 702 according to the DRX configuration514.

For the configuration 700 illustrated in FIG. 7, the power-saving signalconfiguration is activated, i.e., the power-saving signal 522 can betransmitted according to the selective transmission at the radio accessnode 800, and the receiver is enabled according to the selectiveenablement for reception of the power-saving signal 522 at the radiodevice 900. A status 706 of a power supply 708 of the receiver at theradio device 900 is illustrated as a function of time (increasing fromleft to right) in FIG. 7.

If the power-saving signal configuration as part of the DRXconfiguration 500 is activated, the power-saving signal 522 can betransmitted by the radio access node 800 and can be received by theradio device 900 in the steps 306 and 406, respectively. In a firstimplementation compatible with any embodiment, the power saving signal522 is transmitted ahead of each transmission opportunity 702 andindicates whether or not there is data for transmission in the nexttransmission opportunity 702. In a second implementation compatible withany embodiment, the power saving signal 522 is transmitted ahead of thenext transmission opportunity 702 only if there is data 524 or 526 to betransmitted in this transmission opportunity 702. The power-savingsignal 522 according to the second implementation is also referred to asWUS.

The indication of the availability of data for transmission in thepower-saving signal 522 according to the first implementation, or thepresence of the WUS 522 indicating the availability of data fortransmission according to the second implementation, causes the radiodevice 900 to enable its receiver in the step 406 for data reception onthe radio resource 702 according to the DRX configuration message 512,i.e., in the transmission opportunity 702. The radio device 900 maymaintain its receiver enabled for reception in the step 406 afterenabling the receiver in the step 402 or 404. Alternatively, the radiodevice may disable the receiver after the step 402 or 404 for signalreception and re-enable the receiver for data reception in the step 406,e.g., if there is a gap between the radio resource 602 and the radioresource for the power-saving signal 522, or between the radio resourcefor the power-saving signal 522 and the radio resource 702 according tothe DRX configuration, i.e., the transmission opportunity 702.

If DRX is activated and the signal configuration as part of the DRXconfiguration is deactivated, the radio access node 800 does nottransmit the power-saving signal 522 in the step 306, irrespective ofwhether or not there is data 524 or 526 to be transmitted. According tosuch a DRX configuration, the radio device 900 does not expect apower-saving signal 522 and does not enable (i.e., provides no power to)its receiver in the step 406 at the resource of a signal 522. Rather,the radio device 900 enables (i.e., provides power to) its receiver fordecoding, e.g., downlink control information 524, at each transmissionopportunity 702.

Herein, the data may comprise user data 524 and/or control data 526. Forexample, the transmission opportunity 702 may comprise downlink controlinformation (DCI) 524 as control data. If the DCI 524 is indicative of ascheduling assignment, the radio device 900 may continue to receive theuser data 526 according to the scheduling assignment 524.

The power-saving signal configuration 512 may further specify a signallength 714 of the power-saving signal 522. The signal length 714 may becell-specific, e.g., according to a coverage range of the node definedin terms of the MCL. Alternatively or in addition, the signal length 714may be device-specific, e.g., according to a coverage enhancement levelassociated with the radio device. Moreover, a range may be related to aDCI length 716 of the DCI 524 in the radio resource 702 according theDRX configuration 514, i.e., the transmission opportunity 702.

For example, the signal length 714 of the WUS 522 may be at most half or10% of the DCI length 716. The signal length 714 and/or the DCI length716 may be controlled by defining a number of repetitions for thepower-saving signal 522 and/or the DCI 524, respectively. For example,the number of repetitions for the power saving signal 522 may be equalto the number of repetitions for the DCI 524.

In the example for the DRX configuration illustrated in FIG. 7, the DRXconfiguration 700 defines DRX cycles 718 with a DRX cycle length matchedto the periodicity 608 of the synchronization signal configuration 600.That is, the radio resources 702 are periodic with the periodicity 608.In the first and second cycles 718 shown in FIG. 7, the power-savingsignal 522 is indicative of an unavailability of data 524 and 526(according to the first implementation) or the WUS 522 is absent(according to the second implementation). Hence, the radio device 900wakes up (i.e. supplies power to its receiver) for receiving thepower-saving signal 522 and skips the reception in transmissionopportunity 702 according to the step 406, since there is notransmission according to the step 306.

In one embodiment, the technique is applicable to an idle mode operationof the radio device 900 for monitoring paging based on the power-savingsignal 522. The data 524 or 526 comprises a paging message. When thepower-saving signal 522 is activated according to the power-signalconfiguration 512, in every paging cycle 518, the radio device 900 wakesup (at the latest in the step 406) before its designated time window 702(i.e., the transmission opportunity 702 according to the DRXconfiguration 700) to check in the step 406 whether there is DCI 524 fora paging message.

The paging cycle 718 may be configured as DRX cycle or eDRX cycle. ForNB-IoT, the maximum DRX and eDRX cycles are 10.24 seconds and two hours,54 minutes and 46 seconds, respectively. Corresponding maximum numbersfor eMTC is 2.56 seconds for DRX and 43 minutes for eDRX. In a NB-IoTimplementation, the paging message 526 is carried in NPDSCH andscheduled by DCI format N2 carried in NPDCCH 524. In an eMTCimplementation, the paging message 526 is carried in MPDSCH andscheduled by DCI format 6-2 carried in MPDCCH 524.

For radio devices (e.g., UEs) in extreme coverage limited situations, upto 2048 repetitions 716 may be used for transmitting the DCI 524. Thus,a radio device 900 may need to receive as many as 2048 subframes todetermine whether there is a paging message 526 sent on the associatedNPDSCH (e.g., starting 4 NB-IoT subframes from the end of last subframeof the NPDCCH 524). In an eMTC implementation, the MPDSCH may start 2subframes from the end of the last subframe of the MPDCCH 524. By way ofexample, in most DRX or eDRX cycles 718, however, no schedulingassignment (e.g., no DCI format N2) is sent at all during one DRX oreDRX cycle 718. Thus, from a power efficiency point of view, the radiodevice may stay awake in many cases for an unnecessarily long timeattempting to decode the control data (e.g., the scheduling assignment,particularly a DCI format N2). Such waste of energy can be avoided bychanging the power-signal configuration by transmitting thecorresponding control message 512.

FIG. 8 shows a schematic block diagram for an embodiment of the device100. The device 100 comprises one or more processors 804 for performingthe method 300 and memory 806 coupled to the processors 804. Forexample, the memory 806 may be encoded with instructions that implementat least one of the modules 102, 104 and 106.

The one or more processors 804 may be a combination of one or more of amicroprocessor, controller, microcontroller, central processing unit,digital signal processor, application specific integrated circuit, fieldprogrammable gate array, or any other suitable computing device,resource, or combination of hardware, microcode and/or encoded logicoperable to provide, either alone or in conjunction with othercomponents of the device 100 (such as the memory 806), schedulerfunctionality, data transmitter functionality or RAN functionality. Forexample, the one or more processors 804 may execute instructions storedin the memory 806. Such functionality may include providing variousfeatures and steps discussed herein, including any of the benefitsdisclosed herein. The expression “the device being operative to performan action” may denote the device 100 being configured to perform theaction.

As schematically illustrated in FIG. 8, the device 100 may be embodiedby a node 800, e.g., of the RAN. The node 800 comprises a radiointerface 802 coupled to the device 100 for radio communication with oneor more radio devices.

In a variant, the functionality of the device 100 is, e.g., partly orcompletely, provided by another node of the RAN or another node of acore network linked to the RAN. That is, the other node performs themethod 300. The functionality of the device 100 is provided by the othernode to the node 800, e.g., via the interface 802 or a dedicated wiredor wireless interface.

FIG. 9 shows a schematic block diagram for an embodiment of the device200. The device 200 comprises one or more processors 904 for performingthe method 400 and memory 906 coupled to the processors 904. Forexample, the memory 906 may be encoded with instructions that implementat least one of the modules 202, 204 and 206.

The one or more processors 904 may be a combination of one or more of amicroprocessor, controller, microcontroller, central processing unit,digital signal processor, application specific integrated circuit, fieldprogrammable gate array, or any other suitable computing device,resource, or combination of hardware, microcode and/or encoded logicoperable to provide, either alone or in conjunction with othercomponents of the device 100 (such as the memory 906), data receiverfunctionality or radio device functionality. For example, the one ormore processors 904 may execute instructions stored in the memory 906.Such functionality may include providing various features and stepsdiscussed herein, including any of the benefits disclosed herein. Theexpression “the device being operative to perform an action” may denotethe device 200 being configured to perform the action.

The node 900 comprises a radio interface 902 coupled to the device 200for radio communication with at least one of an embodiment of anotherradio device and an embodiment of the radio access node.

An embodiment of a network 1000 is schematically illustrated in FIG. 10.The network 100 comprises a RAN. The RAN comprises at least one cellserved by an embodiment of the radio access node 800. One or moreembodiments of the radio device 900 are located within a coverage rangeof the cell.

The radio access node 800 may be coupled to a core network 1002 of thenetwork 1000.

Time and frequency synchronization contributes to a significant part ofthe total system acquisition time. This holds both for initial cellsearch and system acquisition, as well as for resynchronizationscenarios. While other components, e.g. MIB, SIB1-BR, and SI messageacquisition, can be addressed with improved receiver algorithms andreduced requirements on system information reading, the basic time andfrequency synchronization needs to be done regularly, for example to beable to monitor paging, perform RRM measurements, or perform randomaccess procedures.

Whether or not the synchronization performance using the presentmechanisms is sufficient may depend on assumptions and targetedscenarios. E.g., the maximum supported MCL may differ largely betweendifferent cells, deployments, supported IoT applications, etc.Consequently, it may be difficult to define a fixed enhancedsynchronization signal that provides enough synchronization performancein all types of scenarios without having to specify a very large one,thereby increasing the system overhead in an undesired fashion. Thesolution then is to define an optional enhanced synchronization signalthat can be configured according to the current needs of an individualcell. Some desired basic properties of such a signal can be outlined:

-   -   An enhanced sync signal shall be configurable per cell,        including the possibility to switch it off.    -   The amount of physical resources used shall be configurable.

It is hence beneficial if an enhanced synchronization signal is optionalfor the network, and furthermore configurable per cell with respect toat least the physical resource allocation.

In typical resynchronization scenarios, the timing uncertainty will bemuch smaller. Thus, it is much more efficient if the resynchronizationsignal is concentrated in time such that, e.g., in targeted scenarios,one RSS transmission burst is enough to achieve time and frequencysynchronization. It is herein proposed that this burst duration isconfigurable per cell in order to adjust to different networkdeployments, MCL targets etc. It is also desirable to have theperiodicity of the RSS bursts configurable, both to have control of thesystem overhead, and to cater for different needs, as will be discussedmore below. Hence, in order to have control of the system overhead, andto adjust to different needs, a resynchronization signal (RSS) should beconfigurable both with respect to periodicity of the signal and theamount of time/frequency resources used at each transmission occasion.

An RSS may be configurable in time domain. The frequency location mayalso be configurable, or may be determined by a standard. For example,it could be beneficial to locate an RSS in the center 6 PRBs, therebyopening up for utilizing also the legacy, known PSS/SSS and potentiallyalso the presumably known PBCH to achieve sync faster. However, sincethe center PRBs are fairly occupied already, it may be better to placethe RSS elsewhere. This may be in particular for TDD systems or systemswhere the MBSFN subframes are occupied (e.g. by eMBMS transmission).

In a resynchronization scenario, it is typically assumed that the syncsignal to find is known to the UE, e.g. given by the Cell ID whichdetermines the sequence(s) used for PSS and SSS. However, it is alsopossible that some additional information is conveyed by theresynchronization signal. One example of useful information to convey,in addition to the cell identity, may for example be to indicate thatthe MIB or other system information has changed. This can then furtherbe used by the UE to determine whether some or all MIB and/or SIBreading can be skipped. Similarly, information regarding Extended AccessBarring may be conveyed.

Hence, in addition to a cell identity, the resynchronization signal canbe used convey additional information, such as indication that the MIBor some other system information has changed, or access barringinformation. Since the resynchronization signal is not decoded like in“normal” data transfer, the information would need to be included in theselection or combination of sequences. In this respect, already thesequence selection of the PSS/SSS is a way of encoding the cellidentity. Further information transfer may then be realized e.g. byincreasing the signal space used by the RSS, or by reducing the spaceused to represent the Cell ID and have part of that representing theconveyed additional information instead. It is possible also to conveyinformation by encoding it in terms of using different combinations ofsub-sequences in each transmission burst.

As has become apparent from above description, embodiments of thetechnique enable radio devices to reattach to the network at aconsiderably lower cost compared to existing techniques. A configurablesynchronization signal may be confined into adjacent RBs. Furthermore,the configurability of the configurable synchronization signal allowsthe network to adjust the need and/or cost for providing thesynchronization to its own situation. A network aiming to support radiodevices with extremely low SNR may opt to transmit a more robustconfigurable synchronization signal, but maybe less often, whereasnetworks supporting radio device with moderate SNR may transmit a lessrobust synchronization signal more often. The overhead (e.g., in termsof signaling radio resources) in these two cases can be the same but thenetworks can operate quite differently and be targeting different usecases.

Many advantages of the present disclosure will be fully understood fromthe foregoing description, and it will be apparent that various changesmay be made in the form, construction and arrangement of the units anddevices without departing from the scope of the disclosure and/orwithout sacrificing all of its advantages. Since the disclosure can bevaried in many ways, it will be recognized that the inventionencompasses the scope of the following claims.

The invention claimed is:
 1. A method of providing synchronization witha radio access node for radio communication to one or more radiodevices, the method comprising: transmitting a configuration message toat least one of the radio devices, the configuration message beingindicative of a synchronization signal configuration for a configurablesynchronization signal; wherein the configuration message is indicativeof: a periodicity of transmission occasions of the configurablesynchronization signal; a number of repetitions used in eachtransmission occasion of the configurable synchronization signal; atiming offset for each transmission occasion of the configurablesynchronization signal; and a frequency location of the configurablesynchronization signal in the frequency domain; and transmitting theconfigurable synchronization signal to the at least one radio device inaccordance with the synchronization signal configuration, wherein theconfigurable synchronization signal is indicative of a change in systeminformation and comprises one or more bits indicating whether the systeminformation has been changed during the last X time units, wherein X ispreset in a standardization document.
 2. The method of claim 1, furthercomprising communicating one or more decodable signals between the radioaccess node and the at least one radio device using radio resources inaccordance with the configurable synchronization signal.
 3. The methodof claim 2, wherein the communicating includes broadcasting the one ormore decodable signals comprising system information.
 4. The method ofclaim 2, wherein the one or more decodable signals comprises a wake-upsignal (WUS) and/or a paging message from the radio access node.
 5. Themethod of claim 1, wherein the configuration message, thesynchronization signal configuration, and/or the configurablesynchronization signal is cell-specific.
 6. The method of claim 1,wherein the configurable synchronization signal provides or supports atiming synchronization and/or a frequency synchronization.
 7. The methodof claim 1, wherein repetitions of the configurable synchronizationsignal are arranged according to an aperiodic coding pattern.
 8. Themethod of claim 1, wherein the change in system information is providedby altering a sequence index of the configurable synchronization signal.9. The method of claim 1, wherein the configuration message is furtherindicative of: a length of the configurable synchronization signal inthe time domain; a gap between the repetitions; and/or a bandwidth ofthe configurable synchronization signal in the frequency domain.
 10. Themethod of claim 1, wherein the configurable synchronization signal istransmitted in addition to primary synchronization signals and/orsecondary synchronizing signals transmitted by the radio access node.11. A method of synchronizing a radio device with a radio access nodefor radio communication, the method comprising the radio device:receiving a configuration message from the radio access node, theconfiguration message being indicative of a synchronization signalconfiguration for a configurable synchronization signal; wherein theconfiguration message is indicative of: a periodicity of transmissionoccasions of the configurable synchronization signal; a number ofrepetitions used in each transmission occasion of the configurablesynchronization signal; a timing offset for each transmission occasionof the configurable synchronization signal; and a frequency location ofthe configurable synchronization signal in the frequency domain; andreceiving the configurable synchronization signal from the radio accessnode in accordance with the synchronization signal configuration,wherein the configurable synchronization signal is indicative of achange in system information and comprises one or more bits indicatingwhether the system information has been changed during the last X timeunits, wherein X is preset in a standardization document.
 12. The methodof claim 11, further comprising communicating one or more decodablesignals between the radio access node and the radio device using radioresources in accordance with the configurable synchronization signal.13. The method of claim 12, wherein the communicating includes receivingthe one or more decodable signals comprising system information.
 14. Themethod of claim 13, wherein the radio device only reads the systeminformation in response to the configurable synchronization signal beingindicative of a change in system information.
 15. The method of claim12, wherein the one or more decodable signals comprises a wake-up signal(WUS) and/or a paging message from the radio access node.
 16. The methodof claim 11, wherein the configurable synchronization signal provides orsupports a timing synchronization and/or a frequency synchronization.17. The method of claim 11, wherein repetitions of the configurablesynchronization signal are arranged according to an aperiodic codingpattern.
 18. The method of claim 11, wherein the change in systeminformation is provided by altering a sequence index of the configurablesynchronization signal.
 19. The method of claim 11, wherein an initialaccess of the radio device is based on primary synchronization signalsand/or secondary synchronizing signals and a re-synchronization of theradio device is based on the configurable synchronization signal.
 20. Adevice for providing synchronization with a radio access node for radiocommunication to one or more radio devices, the device comprising:processing circuitry; memory containing instructions executable by theprocessing circuitry whereby the device is operative to: transmit aconfiguration message to at least one of the radio devices, theconfiguration message being indicative of a synchronization signalconfiguration for a configurable synchronization signal; wherein theconfiguration message is indicative of: a periodicity of transmissionoccasions of the configurable synchronization signal; a number ofrepetitions used in each transmission occasion of the configurablesynchronization signal; a timing offset for each transmission occasionof the configurable synchronization signal; and a frequency location ofthe configurable synchronization signal in the frequency domain; andtransmit the configurable synchronization signal to the at least oneradio device in accordance with the synchronization signalconfiguration, wherein the configurable synchronization signal isindicative of a change in system information and comprises one or morebits indicating whether the system information has been changed duringthe last X time units, wherein X is preset in a standardizationdocument.
 21. A device for synchronizing a radio device with a radioaccess node for radio communication, the device comprising: processingcircuitry; memory containing instructions executable by the processingcircuitry whereby the device is operative to: receive a configurationmessage from the radio access node, the configuration message beingindicative of a synchronization signal configuration for a configurablesynchronization signal; wherein the configuration message is indicativeof: a periodicity of transmission occasions of the configurablesynchronization signal; a number of repetitions used in eachtransmission occasion of the configurable synchronization signal; atiming offset for each transmission occasion of the configurablesynchronization signal; and a frequency location of the configurablesynchronization signal in the frequency domain; and receive theconfigurable synchronization signal from the radio access node inaccordance with the synchronization signal configuration, wherein theconfigurable synchronization signal is indicative of a change in systeminformation and comprises one or more bits indicating whether the systeminformation has been changed during the last X time units, wherein X ispreset in a standardization document.